It has been increasingly important to reduce or eliminate emission of hydrocarbon vapors attendant the fueling of vehicles with hydrocarbon fuels, such as liquid gasoline. Certain jurisdictions such as California regulate hydrocarbon emissions to ever decreasing minimums In order to meet various even more restrictive standards, various methods and devices have been proposed. One such prior system includes the use of a vapor recover nozzle such as an assist nozzle associated with a dispenser, an underground storage tank (UST) and a vacuum pump for pumping captured vapors back to the UST. Another system includes the use of a vapor recover nozzle such as a “balance” nozzle associated with a dispenser and a UST where captured vapors passively flow back to the UST. A yet further system includes a vapor recovery nozzle, a dispenser and/or UST, together with dual hydrocarbon filtering canisters operating in a parallel process mode. One canister operates to filter out hydrocarbon vapor emissions from the UST while the other canister is subjected to a reverse air flow to clean or “unload” captured hydrocarbon fractions in it, previously filtered out of a stream of air and vapor discharging from the UST. The canister functions are reversed or cycled as desired for alternate filtering and cleaning, opposite to each other.
It is desired to provide less costly, less complex emissions reducing or eliminating apparatus and methods without the use of vacuum assist at either the fuel nozzle or at any hydrocarbon filter.
Accordingly, it is one objective of the invention to provide improved methods and apparatus for capturing and retaining hydrocarbon emissions resulting from a fueling process from an underground storage tank.
A further objective of the invention has been to provide an improved hydrocarbon filter apparatus and process for filtering hydrocarbons from vapor within an underground storage tank.
A yet further objective of the invention has been to provide passive or balanced apparatus and methods for filtering hydrocarbons from emissions from an underground storage tank of hydrocarbon fuel and for passively cleaning or unloading a hydrocarbon filter without use of any vacuum assist.
A further objective of the invention has been to provide apparatus and processes to filter hydrocarbon emissions resulting from a fueling process with less costly and less complex apparatus and processes than in current use.